79 (number)

Short description: Natural number

| <- 78  | 79 |  80 ->

|
|

← 70 71 72 73 74 75 76 77 78 79 →

List of numbers — Integers

← 0 10 20 30 40 50 60 70 80 90 →

Cardinal| seventy-nine
Ordinal| 79th
(seventy-ninth)
Factorization| prime
Prime| 22nd
Divisors| 1, 79
Greek numeral| ΟΘ´
Roman numeral| LXXIX
Binary| 10011112
Ternary| 22213
Quaternary| 10334
Quinary| 3045
Senary| 2116
Octal| 1178
Duodecimal| 6712
Hexadecimal| 4F16
Vigesimal| 3J20
Base 36| 2736

79 (seventy-nine) is the natural number following 78 and preceding 80.

## Contents

* 1 In mathematics
* 2 In science
* 2.1 In astronomy
* 3 In other fields
* 4 References

## In mathematics

79 is:

* An odd number.
* The smallest number that can not be represented as a sum of fewer than 19 fourth powers.
* The 22nd prime number (between 73 and 83)
* An isolated prime without a twin prime, as 77 and 81 are composite.[1]
* The smallest prime number p for which the real quadratic field Q[√p] has class number greater than 1 (namely 3).[2]
* A cousin prime with 83.
* An emirp in base 10, because the reverse of 79, 97, is also a prime.[3]
* A Fortunate prime.[4]
* A circular prime.[5]
* A prime number that is also a Gaussian prime (since it is of the form 4n \+ 3).
* A happy prime.[6]
* A Higgs prime.[7]
* A lucky prime.[8]
* A permutable prime, with ninety-seven.
* A Pillai prime,[9] because 23! \+ 1 is divisible by 79, but 79 is not one more than a multiple of 23.
* A regular prime.[10]
* A right-truncatable prime, because when the last digit (9) is removed, the remaining number (7) is still prime.
* A sexy prime (with 73).
* The n value of the Wagstaff prime 201487636602438195784363.
* Similarly to how the decimal expansion of 1/89 gives Fibonacci numbers, 1/79 gives Pell numbers, that is, 179=∑n=1∞P(n)×10−(n+1)=0.0126582278… .
* A Leyland number of the second kind.

## In science

* The atomic number of the chemical element gold (Au) is 79.

Signage for table 79 at a restaurant

### In astronomy

* Messier object 79 (M79), a magnitude 8.5 globular cluster in the constellation Lepus
* New General Catalogue object 79 (NGC 79), a galaxy in the constellation Andromeda

## In other fields

See also: List of highways numbered 79

* Live Seventy Nine, an album by Hawkwind
* The years 79 BC, AD 79 or 1979
* The number of the French department Deux-Sèvres
* The ASCII code of the capital letter O

## References

1. ↑ Sloane, N. J. A., ed. "Sequence A007510 (Single (or isolated or non-twin) primes: Primes p such that neither p-2 nor p+2 is prime.)". OEIS Foundation. https://oeis.org/A007510. Retrieved 2022-12-05.
2. ↑ H. Cohen, A Course in Computational Algebraic Number Theory, GTM 138, Springer Verlag (1993), Appendix B2, p.507. The table lists fields by discriminant, which is 4p for Q[√p] when p is congruent to 3 modulo 4, as is the case for 79, so the entry appears at discriminant 316.
3. ↑ "Sloane's A006567 : Emirps". OEIS Foundation. https://oeis.org/A006567.
4. ↑ "Sloane's A046066 : Fortunate primes". OEIS Foundation. https://oeis.org/A046066.
5. ↑ Numbers such that every cyclic permutation is a prime.
6. ↑ "Sloane's A035497 : Happy primes". OEIS Foundation. https://oeis.org/A035497.
7. ↑ "Sloane's A007459 : Higgs' primes". OEIS Foundation. https://oeis.org/A007459.
8. ↑ "Sloane's A031157 : Numbers that are both lucky and prime". OEIS Foundation. https://oeis.org/A031157.
9. ↑ "Sloane's A063980 : Pillai primes". OEIS Foundation. https://oeis.org/A063980.
10. ↑ "Sloane's A007703 : Regular primes". OEIS Foundation. https://oeis.org/A007703.

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